Dropbox is claiming that 'the proposed gag order violates the First Amendment'.

The cloud storage service Dropbox has joined Google, Microsoft, Yahoo, LinkedIn and Facebook in requesting that it be allowed to publish the number of requests for data made by the US government under national security laws.

Dropbox filed a brief with the foreign intelligence surveillance (Fisa) court on Monday expressing support for motions previously filed by Google and others.

The company said it was seeking the court's permission to "publish the number of national-security requests they have received and the number of users affected by those requests".

Dropbox posted the brief online on its transparency report page. It follows motions filed with the Fisa court by Facebook, Google, Microsoft, LinkedIn and Yahoo earlier this month. The companies argued that their inability to make public the number of data requests it receives from the NSA was harming their reputation.

In its brief Dropbox said it has been told by the government that it was not allowed to give the precise number of national-security requests it receives. Dropbox said the only way it can publish the number of such requests is if it combines NSA requests with regular-law enforcement requests, and then rounds the total figure to the nearest thousand.

"Because Dropbox received fewer than 100 regular law-enforcement requests last year, reporting in the government's format would decrease Dropbox's ongoing transparency efforts," the company said.

Dropbox said it had received 87 requests for user information in the US in 2012. The requests specified 164 user accounts. Had Dropbox received "just one national-security request" in 2012, under government stipulations it would mean the company would have to report the number of requests it received for user information as "1-1000".

"Reporting in that way decreases transparency," Dropbox said. "It would shed almost no light on the data requests Dropbox receives, and could foster the impression that Dropbox received many more national-security requests than it did. It would also obfuscate the number of law-enforcement requests Dropbox received in 2012, many of which were not sealed and are in the public record."

"There is no statute, nor any other law, supporting the government's demands," Dropbox said. "To the contrary, the proposed gag order violates the First Amendment, as it interferes with both the public's right to obtain truthful information about a matter of substantial public debate and service providers' rights to publish such information."

Yahoo filed a suit in the Fisa court on 9 September, joining Microsoft, Google and others in an attempt to force the court to allow them to divulge more information and preserve their reputations.

"Yahoo's inability to respond to news reports has harmed its reputation and has undermined its business not only in the United States but worldwide. Yahoo cannot respond to such reports with mere generalities," Yahoo said at the time.